Recently, cold cathodes whish is used as an electron emitting device for emitting electrons are under development in addition to hot cathodes. Electron emitting devices, such as cold cathodes, have an electron emitting part made of molybdenum, carbon nanotube, or diamond, for example. In particular, electron emitting devices having electron emitting parts made of diamond are attractive because the electron affinity of diamond is negative
Patent Document 1 discloses a pn-junction-type electron emitting device as an example of an electron emitting device having an electron emitting part made of diamond. Nonpatent Document 1 discloses an electron emitting device having an electron emitting part and a surface of a metal cathode therein is coated with a diamond film. Nonpatent Document 2 discloses an electron emitting device having a pointed electron emitting part.
Nonpatent Document 3 discloses an electron emitting device having an electron emitting part made of silicon.    Patent Document 1: International Publication No. 93/15522 Pamphlet    Nonpatent Document 1: Journal of Vacuum Science and Technology B14 (1996) 2060    Nonpatent Document 2: Journal of Vacuum Science and Technology B19 (2001) 936    Nonpatent Document 3: Tech. Dig. Int. Electron Devices Meet. (1996), A MOSFET-structure dSi Tip for Stable Emission Current